Fish to save your marbles

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A new French study adds more weight to the theory that eating fish helps stave off dementia.

The seven year study of more than 1600 people aged over 68 years is published in this week's British Medical Journal.

"Elderly people who eat fish or seafood at least once a week are at lower risk of developing dementia, including Alzheimer's disease," write Pascale Barberger-Gateau and colleagues at the Universite Victor Segalen, in Bordeaux.

The researchers found that such people were one third less likely to develop dementia than those who did not consume that level of fish.

Only one in seven of the study group, however, developed dementia over the seven year study period. This means the absolute reduction in risk of developing dementia was from about 12 per cent to 8 per cent.

Other previous studies have suggested education in early life can help prevent dementia. Once the researchers adjusted for differences in education, the link was not so clear.

The researchers suggest the beneficial effect of fish was partly explained by the higher education of those who regularly consume fish.

As well as providing vascular protection, the fatty acids contained in fish oils could reduce inflammation in the brain and may have a specific role in brain development and regeneration of nerve cells.

The authors conclude that healthy dietary habits acquired in infancy could be associated with achievement of higher education. Highly educated people might also adhere more closely to dietary recommendations on fish consumption.

The study also investigated whether eating meat affected the risk of developing dementia and found no significant association.

Study method and limitations

"This is a very interesting and important study," comments Professor Leon Flicker, the chair of the Geriatric Medicine Unit of Royal Perth Hospital.

"It was very well performed and is supportive of the suggestion that some fish in the diet can be of benefit."

But he said more studies were still needed.

While the "observational" study by Barberger-Gateau and colleagues tracked the development of dementia in a given group of elderly people, Professor Flicker said a randomised and controlled "intervention" study would be preferable.

However, he admitted this would be a difficult study to do.

"Can you image getting thousands of people to comply with a study that required them to eat fish or not eat fish at specified times over many years?"